Abstract
Background: The consumption of antioxidant-rich foods can lower the risk of chronic diseases. In the present work, plain yogurt (control) and three kinds of herbal yogurts fortified with a polyphenol extract from nutmeg, black pepper, and white pepper were prepared. Post-acidification, proteolysis, total phenolic content (TPC), and antioxidant activity of yogurt samples were studied over 21 days. Additionally, all yogurt samples were subjected to sensory evaluations on the first day of storage. Results: Higher production (p < 0.05) of lactic acids was observed in all herbal yogurts than in plain yogurt over 21 days of storage. Black pepper and nutmeg enhanced (p < 0.05) the proteolytic activity of yogurt as compared to control, with the maximum values at 21 days. All three herbal yogurts showed the highest TPC (48-55 lg GAE/ml) at day 14 of storage. The radical scavenging activity of yogurt was positively affected (p < 0.05) by the presence of the three kinds of herbal extracts (72-83%; day 0), with the highest values observed in nutmeg yogurt. Ferric reducing antioxidant potential (FRAP) value of nutmeg yogurt was the highest (p < 0.05) among the other samples at day 7 of storage. The ferrous ion chelating (FIC) ability of all the three herbal yogurts ranged from 80% to 83% during 2 weeks. The highest overall preference scores among the three kinds of herbal yogurts were recorded for black pepper yogurt. Conclusions: Polyphenol compounds derived from nutmeg, black pepper, and white pepper extracts could enrich yogurt with antioxidant properties, with nutmeg yogurt showing the best effect.